Integral fuse and switch support for metal-enclosed switch gear

ABSTRACT

High voltage pad-mounted switch gear is provided for three phase loop feeder circuits and fused load circuits. The loop circuits are interconnected by series-connected loop feeder switches. Isolator switches of the telescoping bayonet type are connected between the loop circuit and the fuses. One end of the isolator switch and one end of the fuse are supported by a molded insulator strut. The molded insulator strut has a first hollow turret projection for guiding and supporting one end of the fuse and a second hollow turret projection for supporting the isolator switch. The turret projections enclose the connection between the fuse and the isolator switch thereby providing greater isolation and insulation between the phases of the loop circuits. A tool is provided for removing and inserting the fuse. An interlocking blocking arrangement prevents access to the fuse by the tool until the isolator switch has opened the circuit to the fuse thereby preventing injury to the serviceman and damage to the equipment.

[4 1 Oct. 15,1974

United States Patent [1 1 Bernatt et al.

ABSTRACT High voltage pad-mounted switch gear is provided for three phase loop feeder circuits and fused load circuits. The loop circuits are interconnected by series- Edward J. Rogers, Chicago, both of connected loop feeder switches. isolator switches of the telescoping bayonet type are connected between [73] Asslgnee' S & C Electnc Company Chlcago the loop circuit and the fuses. One end of the isolator switch and one end of the fuse are supported by a molded insulator strut. The molded insulator strut has [22] Filed: Aug. 31, 1973 a first hollow turret projection for guiding and sup- [21] Appl. No.: 393,289

porting one end of the fuse and a second hollow turret projection for supporting the isolator switch. The turret projections enclose the connection between the fuse and the isolator switch thereby providing greater isolation and insulation between the phases of the loop circuits. A tool is provided for removing and inserting References Cited UNITED STATES PATENTS 2,914,627 11/1959 -Eichelberger et 2,914,635 11/1959 Lester et 3,530,406 9/1970 Drager et 3,748,621. 7/1973 Sakats..........

Primary Examiner-J. D. Miller 27 Claims, 14 Drawing Figures Assistant Examiner-Fred E. Bell Attorney, Agent, or Firm-Kirkland & Ellis PATENTEnnm 1 51974 SHEET 8 OF 8 mm mm? INTEGRAL FUSE AND SWITCH SUPPORT FOR METAL-ENCLOSED SWITCH GEAR BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to high voltage metalenclosed switches with drawout fuses, fuse isolator switches and feeder switches, and more particularly, the present invention relates to the combination of a molded insulator strut for a high voltage pad-mounted switch gear and special tools for removing and replacing fuses in a high voltage pad-mounted switch gear.

2. Description of the Prior Art High voltage pad-mounted switch gear arrangements are well known to the art. For example, U.S. Pat. No. 3,576,509 Bernatt invented by a co-inventor of the present application and assigned to the same assignee as the present invention, illustrates one type of prior art metal-enclosed loop switch gear with drawout fuse, fuse isolater switches and ground switches. As pointed out in that patent, metaLenclosed pad-mounted switch gear for distribution of electric power are employed for load circuit protection and sectionalizing loop circuits to isolate faults in servicing. The overall size of the enclosure is important since the size must be consistent with proper spacing between energized elements and between energized elements and ground. A compact construction efficiently utilizing the space within the metal enclosure is of paramount importance. Thus, it is beneficial to maximize the insulation and isolation between the phases of the respective loop circuits to prevent arcing.

Further, since it is desirable to selectively isolate a fuse from its respective loop circuit so that the fuse can be tested and/or replaced without opening the loop circuit, it is desirable to provide isolator switches between the loop circuit and the fuse to interrupt current flow to the electrical load. However, to reduce the duration of electrical are formed with the isolator switch is opened, it is also desirable to provide means for are suppression with the isolator switch. Further, since the distance between the components within the metal enclosure is quite limited, accidental contact with charged portions of the circuitry is possible unless safeguards are provided. Accordingly, it is desirable to provide a means for removing the fuses from the metal enclosure which permits the serviceman to do so without coming into contact with or into proximity to the electrically charged portions of the switch gear.

BRIEF SUMMARY OF THE INVENTION The present invention is an improvement provided in a conventional pad-mounted metal-enclosed switching arrangement comprising an electric power feeder circuit for providing a source of electrical power including feeder circuit conductors, a metal housing having doors therein to permit access to the interior of the housing, an electrical load and a load circuit conductor from the load to a terminal mounted on the housing.

The present invention is an improvement comprising a fuse having first and second ends, a stationary fuse contact mounted within the housing for disengageably engaging the first end of the fuse, the load circuit conductor from the load being connected to the stationary fuse contact. An isolator switch means is connected between the feeder circuit conductor and the fuse so that the isolator switch can interrupt current flow between the feeder circuit conductor and the fuse and thereby isolate the fuse from the source of electrical power. A molded plastic insulator strut is situated within the housing comprising first and second hollow turrets formed in the molded plastic insulator strut. The first hollow turrets are essentially aligned with the stationary contacts so that when a fuse is inserted through a hollow turret, it will engage the corresponding stationary fuse contact. Guide means are provided within the first turrets to electrically engage the second end of the fuse when the first end of the fuse engages the stationary fuse contact. The second turret supports the isolator switch and conductor means interconnect the guide means and the isolator switch so that an electrical circuit is completed to the load when the fuse is inserted and the isolator switch is closed.

An insulated tool means may be provided for engaging the second end of the fuse so that the first end of the fuse can be disengaged from the stationary contact so that the fuse can be removed through the guide means in the first turret. Once removed, the fuse can be tested and if necessary replaced.

Also provided are blocking means for preventing access to the fuse by the tool means until the isolator switch is opened so that the fuse cannot be removed until the electrical circuit to the fuse is broken by the isolator switch. In this manner, accidental injury to the serviceman and damage to the equipment is prevented.

The present invention provides clear advantages over the prior art. The utilization of the molded insulator strut having first and second turret projections increases the insulation and isolation between the respective poles or contacts of each of the phases of the circuit thereby permitting the fuses and switches to be positioned much closer together within the metal enclosure without risk of arcing between phases without requiring the use of insulating barriers between the poles. Further, by utilization of individual isolator switches for each phase, the circuit to an individual fuse for one phase of the three phase system may be interrupted so that that fuse can be removed and tested without breaking the circuit to the other two phases. Thus, unnecessary interruption of service is reduced. However, because of the fact that currents may still be flowing in two of the three fuse circuits, the risk of accidental contact with these phases is increased. Consequently, the tool means of the present invention allows the fuse to be removed without requiring the serviceman to come into contact with the internal portions of the metal enclosure. Further, to prevent inadvertent removal of the fuse while still under load, the blocking means is provided so that the serviceman cannot accidentally disengage a fuse before the isolator switch has isolated fuses from the loop circuit.

Accordingly, it is a primary object of the present invention to provide a metal-enclosed pad-mounted switch gear which permits selective isolation of the drawout fuses from the circuit without having to open the circuit. It is a further object of the present invention to provide a metal-enclosed pad-mounted switch gear with drawout fuses and fuse isolator switched which permits selective isolation of the an individual fuse so that interruption to all the electrical loads is not required to test an individual fuse.

A further object of the present invention is to provide a molded insulator strut for pad-mounted switch gears that will not only support and carry the moving blades of the isolator switch but will also carry the fuse contacts and support and guide the fuse during entry and retractions'.

A further object of the present invention is to provide a metal-enclosed pad-mounted switch gear with drawout fuses and fuse isolator switches having an arc extinguishing structure for each of the stationary contacts of the isolator switch.

A further object of the present invention is to provide an insulated tool for safely unlocking and retracting and/or inserting an individual fuse.

Yet a further object of the present invention is to provide metal-enclosed pad-mounted switch gears with drawout fuses and fuse isolator switches having an interlocking blocking means for preventing access to the fuse by the insulated tool until the fuse has been isolated from the circuit by the isolator switch thereby preventing accidental injury to a serviceman or damage to the equipment.

It is a further object of the present invention to provide gang operation of three isolator switches by a single mechanism where it is required to serve three phase rather than single phase loads.

These and other objects, advantages and features of the present invention will hereinafter appear, and for the purposes of illustration, but not of limitation, exemplary embodiments of the present invention are illustrated in the accompanying drawings.

- BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is an upper left front partially fragmentary perspective view of a preferred embodiment of the present invention.

FIG. 2 is a schematic circuit diagram of a loop circuit having loop feeder switches, isolator switches and drawout fuses in which circuit the present invention could be utilized.

FIG. 3 is a fragmentary partially fragmentary perspective view ofa portion of the preferred embodiment illustrated in FIG. 1.

FIG. 4 is a front view of a portion of the preferred embodiment of the present invention illustrating isolator switches, the molded insulator strut, and the blocking means.

FIG. 5 is a top view of the portion of the embodiment illustrated in FIG. 4 showing the isolator switch open.

. FIG. 6 illustrates an alternative embodiment of the blocking means of the present invention.

FIG. 7 is a plan view of the blocking means illustrated in FIG. 6 with the isolator switch in the closed position, and a phantom view of a second set of isolator switches and fuses.

FIG. 8 is a plan view of an alternative embodiment of a blocking means in accordance with the present invention.

FIG. 9 is a front view of the blocking means illustrated in FIG; 8.

FIG. 10 is a cross-sectional partially fragmentary view of the stationary contact, the fuse, and the fuse removing tool in accordance with the present invention.

FIG. 11 is a partially fragmentary cross-sectional view of the interlocking arrangement for inter-engaging the fuses and the tool.

FIG. 12 is a side view of the stationary fuse contact of the present invention.

FIG. 13 is a cross-sectional view of the interlocking arrangement between the fuse and the tool.

FIG. 14 is a cross-sectional partially fragmentary view of an embodiment of the isolator switch in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to FIG. 1, metal-enclosed switch gear 10 generally comprises metal housing 12 including side panels 13, a top panel 14, a rear panel 15, doors 16, and safety panel 18 having openings 20 therein positioned immediately behind the door 16.

Positioned within housing 12 is interior back wall 22. Mounted on interior back wall 22 are stationary fuse contact assemblies 24 and insulating barriers 26 extending between stationary fuse contact assemblies 24. Fuses 28 are shown engaged at one end by stationary fuse contact assembly 24 andd supported at their opposite end by molded insulator strut 30.

With reference to FIG. 3 molded insulator strut 30 comprises first hollow turret projection 32 adapted to accept an engage fuses 28. Formed in insulator strut 30 essentially perpendicular to first hollow projections 32 are second hollow turret projections 34. Molded insulator strut 39 also comprises annular insulator skirts 36 which separate the respective first and second turret projections.

Second turret projection 34 supports and slidablyengages one end of telescoping blade assembly 40 of isolator switch 42. With reference to FIGS. 3 and 14, isolator switch 42 is of the telescoping blade type. Telescoping blade assembly 40 may be moved in a horizontal direction through second hollow turret projection 34 by insulated operating link 44 which is pivotably mounted to telescoping blade assembly 40 by pin 46. Insulated operating link 44 is actuated by a snap action quick-make, quick-break operating mechanism 48 substantially of the type disclosed in U.S. Pat. No. 3,563,102- Bernatt et al. The structure of operating mechanism 48 will not be described in detail since any type of operating mechanism utilizing a quick-make, quick-break principle may be utilized. In the present invention, a wrench or suitable handle may be used to engage hexagonal rod 49 so that twisting action causes energy to be stored in springs within operating mechanism 48 until molded operating link 40 is snapped in a toggled fashion to either open or close isolator switch 42. Further, a single shaft 49 may be extended through each of the operating mechanisms 48 so that rotation of shaft 49 will actuate all three operating mechanisms 48 simultaneously thereby opening all three isolator switches 42 simultaneously. This structure is advantageous where it is required to serve three phase rather than single phase loads.

With reference to FIG. 14, telescoping blade assembly 40 comprises insulated tube 50 which surrounds moving contact rod 52 and centering guide 54. Insulated tube 50, moving contact rod 52 and centering guide 54 are all keyed together and move as a unit when insulated operating link 44 is pivoted by operating mechanism 48. A stationary contact 56 within sec-.

ond turret projection 34 electrically engages moving contact rod 52 so that moving contact rod 52 can slide through stationary contact 56 without breaking electrical continuity.

Also provided within first turret projection 32 is a fuse contact 58 which slidably engages the one end of fuse 28. Stationary contact 56 and fuse contact 58 are electrically connected.

Moving contact rod 52 has detents 60 and 62 that can be engaged by locking ring 64 positioned within annular groove 66 of liner 68. Liner 68 is adapted to slidably move within insulated tube 50. Provided at the free end of liner 68 are locking pins 70 adapted to engage an annular groove 72 formed in the molded housing 74 of stationary isolator switch contact assembly 76. Attached to the end of moving contact rod 52 is moving contact 78 and trailer 80. Trailer 80 and liner 68 are formed of a suitable arc extinguishing material that forms an arc extinguishing gas upon exposure to an electrical arc.

Stationary isolator switch contact assembly 76 also comprises stationary contact 82 adapted to receive trailer 80 and electrically engage moving contact 78. An arc gas venting chamber 84 filled with a suitable muffler material such as alumina particles is provided to vent the gases created by electrical arcs when stationary contact 82 and moving contact 78 disengage when isolator switch 42 is opened.

Operation of isolator switch 42 is as follows. As operating mechanism 48 causes insulated operating link 44 to rapidly snap to open isolator switch, link 44 causes insulated tube 50, contact rod 52 and centering guide 54 to move as a unit towards the left as viewed in FIG. 14. Locking pins 70 are engaged in annular groove 72 in molded housing 74 thus holding liner 68 in a stationary position. Consequently, locking ring 64 disengages detent 60 as contact rod 52 moves towards the left. As moving contact 78 disengages stationary contact 82, an electrical arc is formed but the arc inhibiting gas created by trailer 80 and liner 68 rapidly extinguishes the arc. The gases created by the are are exhausted through venting chamber 84. When trailer 80 has moved far enough to the left so that turned down portion 81 of trailer 80 will permit locking pins 70 to disengage annular groove 72, liner 68 is released and allowed to move towards the left as locking ring64 engages detent 62. Thus, an air space is established between the molded housing 74 and the end of trailer 80 as operating link 44 completes its travel arc.

During the closing sequence, operating link 44 moves insulated tube 50, moving contact rod 52, and centering guide 54 towards the right as viewed in FIG. 14 until liner 68 engages flange 75 within molded housing 70 thus stopping liner 68. Trailer 80 continues to slide through liner 68 causing locking pins 70 to engage annular groove 72 as turned down portion 81 moves beyond the base of pins 70. Contact rod 52 continues to move towards the right until moving contact 78 approaches stationary contact 82 and a pre-strike arc is formed. However, once again, because of the formation of arc extinguishing gases by trailer 80 and liner 68 the arc is inhibited as contacts 78 and 82 are engaged.

FIG. 2 shows the circuit connections that may be employed in the switch gear 10. isolator switches 42 and fuses 28 are generally schematically illustrated. One side of fuses 28 are respectively connected by conductors to electrical loads (not shown). isolator switches 42 are respectively connected to series conductors 92 by conductors 94. Series conductors 92 serially connect loop feeder switches 96 and 98. Loop feeder swtiches 96 and 98 are connected to loop circuit conductors 97 and 99 respectively. This switching arrangement provides flexibility in the circuit connections. With loop feeder switches 96 and 98 closed, the fuse can be withdrawn for inspection or replacement after the isolator switch 42 has been opened. Thus, the loop circuit need not be opened to inspect the fuses 28. Further, a circuit through the fuse 28 to the electrical load (not shown) may be maintained even if one of the loop feeder switches 96 or 98 is opened to isolate a fault or to permit servicing of that portion of the loop circuit thereto. However, it should be understood that the present invention could be used in conjunction with circuitry of the type shown in H0. 2 wherein conductors 99 and 97 might respectively represent a pair of source feeders, either of which could be selected to supply the load, or which might be paralled in the switch gear. Further, the present invention could be used in conjunction with a circuit which eliminates the switches 96 and 98 and conductors 92 and 94 and directly applies a source of electrical power to isolator switch 42.

With reference to FIGS. 10, 11, 12, and 13, fuse 28 is adapted to engage stationary fuse contact assembly 24 at its distal end with a twist lock action. Formed in the end of fuse 28 is locking groove 100 adapted to engage pin 102 on stationary fuse contact assembly 24.

Stationary fuse contact assembly 24 comprises contact fingers 104 mounted on annular sleeve 106 which is thread mounted on a hollow support 108 attached to exhaust chamber 110. Exhaust chamber 110 is supported by insulator 112 mounted to interior back wall 22 of housing 12. The opposite end of fuse 28 has a ferrule 116 which is engaged by fuse contact 58 within first turret projection 32. Mounted to the end of ferrule 116 is projection 118 having a flange member 120 affixed thereto.

A tool adapted to engage flange member 120 may be provided to facilitate removal and insertion of fuse 28. Tool 130 comprises handle portion 132 and insulator skirt portion 134. in the end of tool 130 is hollow opening 136 adapted to receive flange member 120 when opening 136 and flange member 120 are aligned. A spring 138 biases a sliding member 140 toward opening 136. A recessed groove 142 is provided on the interior surface of the end of tool 130 to engage the edges of flange member 120 after flange member 120 is inserted through opening 136 and handle 130 is rotated 90. Spring 138 and sliding member 140 tend to hold flange member 120 in recessed groove 142. Thus, once tool 130 engages the end of fuse 28, too] 130 can be utilized to rotate fuse 28 to disengage pin 102 from locking groove 100 in the distal end of fuse 28 so that fuse 28 can be removed. Once disengaged, fuse 28 can be withdrawn through first turret projection 32 by sliding through contact 58 until fuse 28 is withdrawn through opening 20 in safety panel 18.

With reference to FIGS. 4, 5, 6, and 7, a blocking arrangement may be incorporated with the present invention to prevent the tool 130 from being inserted through opening 20 in safety panel 18 until isolator switch 42 has been operated to break the circuit to fuse 28.

Blocking arrangement 150 comprises an arm 152 attached to hexagonal shaft 49 on operating mechanism 48 so that when hexagonal shaft 49 is rotated, arm 152 is pivoted. Pivotably connected to the end of arm 152 is linkage member 154. Linkage member 154 is connected to pivot member 156 which is pivotably mounted on support 158 so that it can pivot freely. The

opposite end of pivot member 156 is pivotably mounted to blocking member 160 which slides in guide 162 in essentially a horizontal direction.

When isolator switch 42 is closed (see FIGS. 4 8L 7) blocking member 160 is moved across opening in safety panel 18 thus preventing the insertion of tool 130. However, as hexagonal shaft 49 is rotated to cause operating mechanism 48 to open isolator switch 42, arm 152 is pivoted to cause pivot member 156 to rotate thus moving blocking member 160 away from opening 20 in safety panel 18. Consequently, when isolator switch 42 is opened, tool 130 can be inserted through opening 20 to engage the end of fuse 28 so that fuse 28 can be removed for testing and/or replacement. Thus, blocking arrangement 150 prevents accidental removal of fuse 28 while fuse 28 is connected to loop feeder circuit thereby preventing accidental injury to the serviceman or damage to the equipment as a result of arcing when the distal end of fuse 28 disengages stationary fuse contact assembly 24.

With reference to FIGS. 8 and 9, an alternative embodiment of a blocking arrangement 170 is illustrated. In this embodiment, an arm 172 is attached to hexagonal shaft 49 so that when hexagonal shaft 49 is rotated to open or close isolator switch 42, arm 172 is pivoted. Arm 172 is pivotably connected to a linkage member 174, and linkage member 174 is pivotably connected to pivot member 176, aand also to arm 178. Arm 178 is rigidly attached to shaft 180 so that when arm 178 pivots, shaft 180 rotates causing arm 182 attached to the bottom of shaft 180 to pivot. Arm 182 is pivotably attached to a connecting linkage member 184. Linkage member 184 is pivotably attached to arm 186 which is rigidly attached to arm 188 so that arms 186 and 188 pivot about pin 189 when linkage member 184 is moved in a horizontal direction. Arm 188 is connected to linkage member 190 at one end and linkage member 190 is also connected to arm 192 rigidly attached to tongue 194 so that arm 192 and tongue 194 pivot as a unit around shaft 196. A load-break connecter 200 is disengageably connected to a terminal 202 so that the circuit to the electrical load (not shown) can be disconnected by removing load-break connecter 200. When load-break connecter 200 is connected to terminal 202, tongue 194 is in the position shown by the dotted lines in FIG. 8. In this position, the direct linkage between tongue 194 and arm 172 prevents hexagonal shaft 49 from being rotated until load-break connecter 200 is disconnected from terminal 202. However, once load-break connecter 200 is disconnected from terminal 202, tongue 194 can pivot freely thus allowing hexagonal shaft 49 to be rotated so that arm 172 can pivot and linkage member 174 can be moved to cause pivot member 176 to pivot about support 206. Pivot member 176 is connected to blocking member 208 which slides horizontally through guide 210 when isolator switch 42 is opened to allow tool 130 to be inserted through opening 20 in safety panel 18.

Thus, in blocking arrangement 170, it is impossible to insert tool 130 through opening 20 in safety panel 18 to engage and remove fuse 28 until load-break connecter 200 is disengaged from terminal 202 and isolator switch 42 is open. Consequently, in this embodiment, fuse 28 is totally isolated from both the loop feeder circuit and the electrical load before fuse 28 can be removed. This embodiment has particular advantages where the load connected to load-break connector 200 may remain charged, for example, by a capacitor or bank of capacitors. Thus, accidential injury or damage may be avoided. It should be noted that when load-break connectors 200 are provided, the respective isolator switches need only provide an isolating or disconnecting function and the current interrupting features may be omitted.

It should be evident from the foregoing, that the present invention can be varied and modified in many respects. For example, as shown in FIG. 7, by enlarging housing 12, an additional isolator switch, insulator strut and fuses may be provided so that additional electrical loads may be connected to the loop feeder circuit. In addition, a variety of blocking arrangements and tools may be utilized in the present invention to achieve the same result as the tools and blocking arrangements discussed herein. Moreover, while the telescoping isolator switch 42 of the present invention is particularly advantageous because of its compact operating structure, many types of isolator switches may be utilized.

Accordingly, it should be understood that various changes, modifications, and variations in the structure and function of the present invention may be effected without departing from the spirit and scope of the present invention as defined in the appended claims.

We claim: 1. In a metal-enclosed circuit switching arrangement comprising feeder circuit conductors for providing a source of electrical power, load circuit conductors to an electrical load, a metal housing enclosing said conductors, whereby the improvement comprises:

a fuse having first and second ends; a stationary fuse contact means mounted in the housing for disengageably engaging the first end of the fuse, a load circuit conductor being connected to said stationary fuse contact means; isolator switch means mounted in the housing, a

feeder circuit conductor being electrically connected to said isolator switch means; a molded plastic insulator strut comprising:

first and second hollow turrets, said first turret being essentially aligned with said stationary fuse contact means;

guide means within said first turret for electrically engaging the second end of said fuse when the first end of said fuse engages said stationary fuse contact means;

switch contact means within said second turret for engaging and supporting said isolator switch means;

means for electrically interconnecting said guide means and said switch contact means so that an electrical circuit is completed between the feeder circuit connector and the load connector when said fuse is engaged by said stationary'contact means and said guide means, and said isolator switch means is closed.

2. An improvement, as claimed in claim 1, further comprising:

an insulated tool means for engaging the second end of said fuse so that said tool means can be actuated to disengage said fuse from said stationary fuse contact means and said guide means so that said fuse can be removed for testing and replacement.

3. An improvement, as claimed in claim 2, further comprising:

blocking means for preventing access to said fuse by said tool means until said isolator switch means is opened so that said fuse cannot be removed until the electrical circuit from the feeder circuit conductor to said fuse is broken.

4. An improvement, as claimed in claim 1, wherein said isolator switch means comprises:

a linear reciprocating contact arm slidably mounted and supported by said turret contact means in said second turret, said contact arm being movable between a first and a second position;

a stationary switch contact mounted in line with said contact arm so that said contact arm electrically connects said stationary switch contact when said contact arm is in its first position and electrically disconnects said stationary switch contact when said contact arm is in its second position.

5. An improvement, as claimed in claim 4, wherein said contact arm further comprises:

a contact member attached to the end of said contact arm;

a trailer member attached to the end of said contact member fonned of a material capable of producing an arc quenching gas when exposed to an electrical arc.

6. An improvement, as claimed in claim 5, wherein said stationary switch contact further comprises:

a hollow receptacle for receiving said contact member and said trailer;

an annular contact within said hollow receptacle for electrically engaging said contact member said annular contact being connected to the feeder circuit conductor;

a muffler means communicating with said hollow receptacle for exhausting and cooling any gases created by are formation as said annular contact and contact member disengage and engage under electrical load.

7. An improvement, as claimed in claim 2, further comprising:

a load-break connecter connected between said stationary contact and the load circuit conductor, said load-break connecter being disconnectable from said stationary fuse contact means to break the electrical circuit to the electrical load.

8. An improvement, as claimed in claim 7, further comprising blocking means operably connected to said load-break connecter for preventing access to said fuse by said tool means until said load-break connecter is disconnected from said stationary fuse contact means.

9. An improvement, as claimed in claim 8, wherein said blocking means further comprises:

interconnecting means for preventing access to said fuse by said tool until said isolator switch means interrupts the circuit to the feeder circuit conductor.

10. An improvement, as claimed in claim 3, further comprising:

a panel member positioned adjacent said molded plastic insulator strut inside a door of the metal housing, said panel member having openings in line with said first turrets dimensioned to permit said tool to be inserted through said openings, and said blocking means comprises cover means for covering said openings to prevent insertion of said tool and uncovering said openings in response to said isolator switch means interrupting the circuit between the feeder circuit conductor and said fuse. 11. An improvement, as claimed in claim 1, wherein said fuse comprises:

a cylindrical housing having contact engaging means at the first end thereof for disengageably engaging the stationary fuse contact means, said cylindrical housing dimensioned to be accepted and guided by said guide means in said first turret so that when said fuse is inserted into said guide means said engaging means is aligned with stationary contact means and will engage said stationary fuse contact means when the second end of said fuse electrically engages said guide means. 12. An improvement, as claimed in claim 2, wherein said tool means comprises a hollow end portion for receiving an engaging the second end of the fuse and a handle means opposite the hollow end portion.

13. An improvement, as claimed in claim 1, wherein said fuse engages said stationary fuse contact means with a twist lock action.

14. In a pad-mounted metaLenclosed loop circuit switching arrangement comprising a loop electric power supply circuit conductor adapted to be energized from either or both ends, first and second loop feeder switches connected in series to said loop circuit conductor, series conductor means connecting said loop feeder switches in series whereby on closure thereof the loop circuit extends therethrough, a metal housing enclosing the first and second loop feeder switches and the series conductor means having doors therein to permit access to the interior of the housing, an electrical load, and a conductor from the load to the housing; wherein the improvement comprises:

a fuse having first and second ends; a stationary fuse contact means mounted in the housing for disengageably engaging the first end of the fuse, the conductor from the load being connected to said stationary fuse contact means; isolator switch means being connected to the series conductor means for interrupting a circuit to said series conductor means; a molded plastic insulator strut comprising:

first and second hollow turrets, said first turret being essentially aligned with said stationary fuse contact means;

guide means within said first turret for electrically engaging the second end of said fuse when the first end of said fuse engages said stationary fuse contact means;

turret contact means within said second turret for engaging and supporting said isolator switch means;

means for electrically interconnecting said guide means and said turret contact means so that an electrical circuit is completed to the load when said fuse is engaged by said stationary contact means and said guide means, and said isolator switch means is closed.

15. An improvement, as claimed in claim 14, further comprising:

an insulated tool means for engaging the second end of said fuse so that said tool means can be actuated to disengage said fuse from said stationary fuse contact means and said guide means so that said fuse can be removed for testing and replacement.

16. An improvement, as claimed in claim 15, further comprising:

blocking means for preventing access to said fuse by said tool means until said isolator swtich means is opened so that saidfuse cannot be removed until the electrical circuit from the loop circuit to said fuse is broken.

17. An improvement, as claimed in claim 14, wherein said isolator switch means comprises:

a linear reciprocating contact arm slidably mounted and supported by said turret contact means in said second turret, said contact arm being movable between a first and a second positions;

a stationary switch contact mounted in line with said contact arm so that said contact arm electrically connects said stationary switch contact when said contact arm is in its first position and electrically disconnects said stationary switch contact when said contact arm is in its second position.

18. An improvement, as claimed in claim 17, wherein said contact arm further comprises:

a contact member attached to the end of said contact arm;

a trailer member attached to the end of said contact member formed of a material capable of producing an arc quenching gas when exposed to an electrical arc.

19. An improvement, as claimed in claim 18, wherein said stationary switch contact further comprises:

'a hollow receptacle for receiving said contact member and said trailer;

an annular contact within said hollow receptacle for electrically engaging said contact member;

a muffler means communicating with said hollow receptacle for exhausting and cooling any gases created by arc formation as said annular contact and contact member disengage and engage under electrical load.

20. An improvement, as claimed in claim 15, further comprising:

a load-break connecter connected between said stationary contact and the electrical load, said loadbreak connecter being disconnectable from said stationary fuse contact means to break the electrical circuit to the electrical load.

21. An improvement, as claimed in claim 20, further comprising blocking means operably connected to said load-break connecter for preventing access to said fuse by said tool means until said load-break connecter is disconnecter from said stationary fuse contact means.

22. An improvement, as claimed in claim 21, wherein said blocking means further comprises:

interconnecting means for preventing access to said fuse by said tool until said isolator switch means interrupts the circuit to said series conductor means.

23. An improvement, as claimed in claim 16, further comprising:

a panel member positioned adjacent said molded plastic insulator strut inside one of the doors of the metal housing said panel member having openings in line with said first turrets dimensioned to permit said tool to be inserted through said openings, and

said blocking means comprises cover means for covering said openings to prevent insertion of said tool and uncovering said openings in response to said isolator switch means interrupting the circuit between the series conductor means and said fuse.

24. An improvement, as claimed in claim 14, wherein said fuse comprises:

a cylindrical housing having contact engaging means at the first end thereof for disengageably engaing the stationary fuse contact means, said cylindrical housing being dimensioned to be accepted and guided by said guide means in said first turret so that when said fuse is inserted into said guide means said engaging means is aligned with said stationary contact means and will engage said stationary fuse contact means when the second end of said fuse electrically engages said guide means.

25. An improvement, as claimed in claim 15, wherein said tool means comprises a hollow end portion for receiving and engaging the second end of the fuse and a handle means opposite the hollow end portion.

26. An improvement, as claimed in claim 14, wherein said fuse engages said stationary fuse contact means with a twist lock action.

27. In a metal-enclosed circuit switching arrangement comprising feeder circuit conductors for providing a source of electrical power, load circuits conductors to an electrical load, a metal housing enclosing said conductors, whereby the improvement comprises:

a removable conductor means having first and second ends; a stationary contact means mounted in the housing for disengageably engaging the first end of the conductor means, a load circuit conductor being connected to said stationary contact means; isolator switch means mounted in the housing, a

feeder circuit conductor being electrically connected to said isolator switch means; a molded plastic insulator strut comprising:

first and second hollow turrets, said first turret being essentially aligned with said stationary contact means;

guide means within said first turret for electrically engaging the second end of said conductor means when the first end of said conductor means engages said stationary contact means;

switch contact means within said second turret for engaging and supporting said isolator switch means; and

means for electrically interconnecting said guide means and said switch contact means so that an electrical circuit is completed between the feeder circuit connector and the load connector when said conductor means is engaged by said stationary contact means and said guide means, and said isolator switch means is closed. 

1. In a metal-enclosed circuit switching arrangement comprising feeder circuit conductors for providing a source of electrical power, load circuit conductors to an electrical load, a metal housing enclosing said conductors, whereby the improvement comprises: a fuse having first and second ends; a stationary fuse contact means mounted in the housing for disengageably engaging the first end of the fuse, a load circuit conductor being connected to said stationary fuse contact means; isolator switch means mounted in the housing, a feeder circuit conductor being electrically connected to said isolator switch means; a molded plastic insulator strut comprising: first and second hollow turrets, said first turret being essentially aligned with said stationary fuse contact means; guide means within said first turret for electrically engaging the second end of said fuse when the first end of said fuse engages said stationary fuse contact means; switch contact means within said second turret for engaging and supporting said isolator switch means; means for electrically interconnecting said guide means and said switch contact means so that an electrical circuit is completed between the feeder cIrcuit connector and the load connector when said fuse is engaged by said stationary contact means and said guide means, and said isolator switch means is closed.
 2. An improvement, as claimed in claim 1, further comprising: an insulated tool means for engaging the second end of said fuse so that said tool means can be actuated to disengage said fuse from said stationary fuse contact means and said guide means so that said fuse can be removed for testing and replacement.
 3. An improvement, as claimed in claim 2, further comprising: blocking means for preventing access to said fuse by said tool means until said isolator switch means is opened so that said fuse cannot be removed until the electrical circuit from the feeder circuit conductor to said fuse is broken.
 4. An improvement, as claimed in claim 1, wherein said isolator switch means comprises: a linear reciprocating contact arm slidably mounted and supported by said turret contact means in said second turret, said contact arm being movable between a first and a second position; a stationary switch contact mounted in line with said contact arm so that said contact arm electrically connects said stationary switch contact when said contact arm is in its first position and electrically disconnects said stationary switch contact when said contact arm is in its second position.
 5. An improvement, as claimed in claim 4, wherein said contact arm further comprises: a contact member attached to the end of said contact arm; a trailer member attached to the end of said contact member formed of a material capable of producing an arc quenching gas when exposed to an electrical arc.
 6. An improvement, as claimed in claim 5, wherein said stationary switch contact further comprises: a hollow receptacle for receiving said contact member and said trailer; an annular contact within said hollow receptacle for electrically engaging said contact member said annular contact being connected to the feeder circuit conductor; a muffler means communicating with said hollow receptacle for exhausting and cooling any gases created by arc formation as said annular contact and contact member disengage and engage under electrical load.
 7. An improvement, as claimed in claim 2, further comprising: a load-break connecter connected between said stationary contact and the load circuit conductor, said load-break connecter being disconnectable from said stationary fuse contact means to break the electrical circuit to the electrical load.
 8. An improvement, as claimed in claim 7, further comprising blocking means operably connected to said load-break connecter for preventing access to said fuse by said tool means until said load-break connecter is disconnected from said stationary fuse contact means.
 9. An improvement, as claimed in claim 8, wherein said blocking means further comprises: interconnecting means for preventing access to said fuse by said tool until said isolator switch means interrupts the circuit to the feeder circuit conductor.
 10. An improvement, as claimed in claim 3, further comprising: a panel member positioned adjacent said molded plastic insulator strut inside a door of the metal housing, said panel member having openings in line with said first turrets dimensioned to permit said tool to be inserted through said openings, and said blocking means comprises cover means for covering said openings to prevent insertion of said tool and uncovering said openings in response to said isolator switch means interrupting the circuit between the feeder circuit conductor and said fuse.
 11. An improvement, as claimed in claim 1, wherein said fuse comprises: a cylindrical housing having contact engaging means at the first end thereof for disengageably engaging the stationary fuse contact means, said cylindrical housing dimensioned to be accepted and guided by said guide means in said first turret so that when said fuse is inserted into said guide meaNs said engaging means is aligned with stationary contact means and will engage said stationary fuse contact means when the second end of said fuse electrically engages said guide means.
 12. An improvement, as claimed in claim 2, wherein said tool means comprises a hollow end portion for receiving an engaging the second end of the fuse and a handle means opposite the hollow end portion.
 13. An improvement, as claimed in claim 1, wherein said fuse engages said stationary fuse contact means with a twist lock action.
 14. In a pad-mounted metal-enclosed loop circuit switching arrangement comprising a loop electric power supply circuit conductor adapted to be energized from either or both ends, first and second loop feeder switches connected in series to said loop circuit conductor, series conductor means connecting said loop feeder switches in series whereby on closure thereof the loop circuit extends therethrough, a metal housing enclosing the first and second loop feeder switches and the series conductor means having doors therein to permit access to the interior of the housing, an electrical load, and a conductor from the load to the housing; wherein the improvement comprises: a fuse having first and second ends; a stationary fuse contact means mounted in the housing for disengageably engaging the first end of the fuse, the conductor from the load being connected to said stationary fuse contact means; isolator switch means being connected to the series conductor means for interrupting a circuit to said series conductor means; a molded plastic insulator strut comprising: first and second hollow turrets, said first turret being essentially aligned with said stationary fuse contact means; guide means within said first turret for electrically engaging the second end of said fuse when the first end of said fuse engages said stationary fuse contact means; turret contact means within said second turret for engaging and supporting said isolator switch means; means for electrically interconnecting said guide means and said turret contact means so that an electrical circuit is completed to the load when said fuse is engaged by said stationary contact means and said guide means, and said isolator switch means is closed.
 15. An improvement, as claimed in claim 14, further comprising: an insulated tool means for engaging the second end of said fuse so that said tool means can be actuated to disengage said fuse from said stationary fuse contact means and said guide means so that said fuse can be removed for testing and replacement.
 16. An improvement, as claimed in claim 15, further comprising: blocking means for preventing access to said fuse by said tool means until said isolator swtich means is opened so that said fuse cannot be removed until the electrical circuit from the loop circuit to said fuse is broken.
 17. An improvement, as claimed in claim 14, wherein said isolator switch means comprises: a linear reciprocating contact arm slidably mounted and supported by said turret contact means in said second turret, said contact arm being movable between a first and a second positions; a stationary switch contact mounted in line with said contact arm so that said contact arm electrically connects said stationary switch contact when said contact arm is in its first position and electrically disconnects said stationary switch contact when said contact arm is in its second position.
 18. An improvement, as claimed in claim 17, wherein said contact arm further comprises: a contact member attached to the end of said contact arm; a trailer member attached to the end of said contact member formed of a material capable of producing an arc quenching gas when exposed to an electrical arc.
 19. An improvement, as claimed in claim 18, wherein said stationary switch contact further comprises: a hollow receptacle for receiving said contact member and said trailer; an annular contact within said Hollow receptacle for electrically engaging said contact member; a muffler means communicating with said hollow receptacle for exhausting and cooling any gases created by arc formation as said annular contact and contact member disengage and engage under electrical load.
 20. An improvement, as claimed in claim 15, further comprising: a load-break connecter connected between said stationary contact and the electrical load, said load-break connecter being disconnectable from said stationary fuse contact means to break the electrical circuit to the electrical load.
 21. An improvement, as claimed in claim 20, further comprising blocking means operably connected to said load-break connecter for preventing access to said fuse by said tool means until said load-break connecter is disconnecter from said stationary fuse contact means.
 22. An improvement, as claimed in claim 21, wherein said blocking means further comprises: interconnecting means for preventing access to said fuse by said tool until said isolator switch means interrupts the circuit to said series conductor means.
 23. An improvement, as claimed in claim 16, further comprising: a panel member positioned adjacent said molded plastic insulator strut inside one of the doors of the metal housing said panel member having openings in line with said first turrets dimensioned to permit said tool to be inserted through said openings, and said blocking means comprises cover means for covering said openings to prevent insertion of said tool and uncovering said openings in response to said isolator switch means interrupting the circuit between the series conductor means and said fuse.
 24. An improvement, as claimed in claim 14, wherein said fuse comprises: a cylindrical housing having contact engaging means at the first end thereof for disengageably engaing the stationary fuse contact means, said cylindrical housing being dimensioned to be accepted and guided by said guide means in said first turret so that when said fuse is inserted into said guide means said engaging means is aligned with said stationary contact means and will engage said stationary fuse contact means when the second end of said fuse electrically engages said guide means.
 25. An improvement, as claimed in claim 15, wherein said tool means comprises a hollow end portion for receiving and engaging the second end of the fuse and a handle means opposite the hollow end portion.
 26. An improvement, as claimed in claim 14, wherein said fuse engages said stationary fuse contact means with a twist lock action.
 27. In a metal-enclosed circuit switching arrangement comprising feeder circuit conductors for providing a source of electrical power, load circuits conductors to an electrical load, a metal housing enclosing said conductors, whereby the improvement comprises: a removable conductor means having first and second ends; a stationary contact means mounted in the housing for disengageably engaging the first end of the conductor means, a load circuit conductor being connected to said stationary contact means; isolator switch means mounted in the housing, a feeder circuit conductor being electrically connected to said isolator switch means; a molded plastic insulator strut comprising: first and second hollow turrets, said first turret being essentially aligned with said stationary contact means; guide means within said first turret for electrically engaging the second end of said conductor means when the first end of said conductor means engages said stationary contact means; switch contact means within said second turret for engaging and supporting said isolator switch means; and means for electrically interconnecting said guide means and said switch contact means so that an electrical circuit is completed between the feeder circuit connector and the load connector when said conductor means is engaged by said stationary contact means and said guide means, and said isolatoR switch means is closed. 